1. Field of the Invention
The present invention relates to a communications assembly and a method for exchanging data.
2. Description of the Related Art
In the field of automotive engineering, serial interfaces (for example, SPI, serial peripheral interface) are used in control units for data transmission between logic modules which may be designed as integrated circuits (IC), for example. The SPI standard describes a bidirectional, synchronous and serial data transmission between a module designated as a master and various modules designated as slaves. An interface includes at least three lines between the master and a slave, generally two data lines and one clock line. When there are multiple slaves, each of these modules requires an additional selection line from the master. The SPI interface permits the implementation of a daisy chain or bus topology.
In some cases, the SPI interface is not suitable for transmission of time-critical trigger signals to meet the real-time requirements of today's safety-critical applications. Frequently there is merely an exchange of diagnostic and status information using an SPI. Time-critical trigger signals are generally transmitted to the trigger modules of the actuators and/or evaluation circuits of the sensors using timer units and/or proprietary interfaces with great complexity.
The use of the SPI interface in the form of a bus topology results in progressively worse signal integrities at higher data rates and strong interference effects due to inferior EMC properties. In addition, only the transmission signal is transmitted in synchronization with the clock signal, whereas the phase-locked transmission of the reception signal becomes increasingly more difficult at high data rates due to the internal lag times in the slave, possibly causing errors in the data transmission. When using the SPI interface in a daisy-chain topology, i.e., in a ring topology, very long latency times occur, which is why such a configuration cannot be used efficiently in automotive control units.
According to the related art, an SPI interface offers no possibility for transmission of interrupts (interrupt queries) to the master. For this purpose, the SPI master must pose a query to the slave at defined intervals, for example, a read command for readout of new data (so-called polling). Another remedy is offered by an additional interrupt line, but this increases the wiring complexity and the number of pins, so it is not economical.